U.S. patent application number 09/835658 was filed with the patent office on 2001-08-16 for in-situ drilling system with dust collection and overload control.
Invention is credited to Hinshaw, Gregory E., McIntyre, William S. JR., Wilson, Henry E..
Application Number | 20010013426 09/835658 |
Document ID | / |
Family ID | 22732918 |
Filed Date | 2001-08-16 |
United States Patent
Application |
20010013426 |
Kind Code |
A1 |
Wilson, Henry E. ; et
al. |
August 16, 2001 |
In-situ drilling system with dust collection and overload
control
Abstract
An apparatus and method is provided for substantially
continuously drilling and disposing of drill cuttings and dust to
minimize airborne contamination while providing protection against
overload. A drill stem with a bit is advanced by a drill head to
form the drill hole. A flushing mechanism utilizes vacuum or
pressurized water for flushing the cuttings and dust from the drill
hole for disposal. A transducer monitors at least one parameter of
the fluid flow. A controller is utilized to regulate the rate of
drilling dependent on the signal level of the parameter being
monitored.
Inventors: |
Wilson, Henry E.; (Ironton,
OH) ; Hinshaw, Gregory E.; (Proctorville, OH)
; McIntyre, William S. JR.; (Proctorville, OH) |
Correspondence
Address: |
KING & SCHICKLI, PLLC
247 NORTH BROADWAY
LEXINGTON
KY
40507
US
|
Family ID: |
22732918 |
Appl. No.: |
09/835658 |
Filed: |
April 16, 2001 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
09835658 |
Apr 16, 2001 |
|
|
|
09198327 |
Nov 24, 1998 |
|
|
|
6216800 |
|
|
|
|
Current U.S.
Class: |
175/48 ; 175/207;
175/40; 175/65 |
Current CPC
Class: |
E21B 21/07 20130101;
E21B 21/065 20130101; B23Q 15/013 20130101; B23Q 11/005 20130101;
G05B 2219/42289 20130101; B23Q 17/00 20130101; B23Q 11/04 20130101;
E21B 44/02 20130101; G05B 19/4062 20130101; E21B 21/08 20130101;
B23Q 11/0046 20130101 |
Class at
Publication: |
175/48 ; 175/40;
175/65; 175/207 |
International
Class: |
E21B 047/00 |
Claims
In the claims:
1. An apparatus for substantially continuously forming a drill hole
in the earth using a drill stem having a bit while flushing of the
cuttings and dust from the drill hole, comprising: a drill head
with a feed device for feeding the drill stem and bit to form the
drill hole; a flushing mechanism for flushing the cuttings and dust
from the hole adjacent the stem by bailing fluid flow so as to
substantially eliminate airborne contamination; a transducer
monitoring at least one parameter of the fluid flow and generating
a signal indicative of the level of said parameter; a drive unit
for establishing a rate of driving for the drill stem and bit; and
a controller responsive to the signal from said transducer
indicative of said pressure for substantially constantly regulating
the rate of driving and feed; whereby said cuttings and dust are
flushed in a controlled manner to substantially eliminate airborne
contamination and provide the substantially continuous and optimum
drilling operation.
2. The apparatus of claim 1, wherein said flushing mechanism
includes a vacuum generator and includes a transfer duct for
conveying said flow to a remote location; said transducer being for
sensing the negative gauge pressure in said duct and supplying a
corresponding signal to said controller; said controller serving to
regulate the rate of driving and feed of the drill stem dependent
on a level of the signal indicative of the negative gauge pressure
maintained in said duct.
3. The apparatus of claim 2, wherein said transducer is operative
to sense the negative gauge pressure during conveying of said
cuttings and dust by the vacuum through the flushing mechanism.
4. The apparatus of claim 2, wherein said vacuum generator includes
a blower to generate a vacuum on an intake side, said duct serving
to convey said cuttings and dust being coupled to the intake side
thereof.
5. The apparatus of claim 1, wherein said controller is
programmable to allow adjustment of an approaching overload and
reset threshold as determined by the parameter of the fluid flow
for establishing the optimum rate of driving and feed for said
drill stem.
6. The apparatus of claim 5, wherein said drive unit is rotary and
said drill stem is adapted for rotary driving motion, said
controller being operative for regulating the speed of rotary
driving of the drill stem dependent on said signal.
7. The apparatus of claim 1, wherein a passage is provided in said
drill stem and bit for the flow of said fluid, cuttings and dust,
and said flushing mechanism further includes a transfer duct for
conveying the cuttings and dust from said passage to a remote
location.
8. The apparatus of claim 1, wherein said flushing mechanism
includes a hydraulic pump for forcing pressurized water through the
mechanism to generate a slurry with said cuttings and dust for
deposit outside said drill hole.
9. The method of substantially continuously drilling a drill hole
in the earth using a drill stem and bit while flushing the cuttings
and dust from the hole comprising the steps of: driving and feeding
the drill stem and bit in the earth to form the drill hole;
flushing the cuttings and dust from the hole by bailing fluid flow
so as to substantially eliminate airborne contamination; monitoring
at least one parameter of the fluid flow; and substantially
constantly regulating the rate of driving and feed of said drill
stem and bit based on the monitoring of the parameter; whereby said
cuttings and dust are flushed in a controlled manner to
substantially eliminate airborne contamination and provide a
substantially continuous and optimum drilling operation.
10. The method of claim 9, wherein said flushing is by vacuum and
the flow parameter being monitored is the negative gauge pressure;
and regulating the rate of driving and feed of the drill stem
establishes the optimum driving and feed rate dependent on the
negative gauge pressure created during the step of flushing said
cuttings and dust.
11. The method of claim 10, wherein is further provided the step of
adjusting the threshold of the negative gauge pressure establishing
said optimum rate of driving and feed for said drill stem.
12. The method of claim 11, wherein the adjusting step is performed
by setting the threshold level in the range of 10% to 20% above the
normal level of negative gauge pressure and to reset the pressure
level for the flushing step to normal within the range of 0.5-4
inches Hg. once a threat of overload is past.
13. The method of claim 9, wherein the step of driving includes
rotary driving of said stem and regulating the speed of rotary
driving of the drill stem depending on a level of the monitored
parameter.
14. The method of claim 9, wherein the substantially constantly
regulating step for the driving rate is performed by slowing the
feed of said drill stem to maintain the substantially continuous
and optimum driving rate of said drill stem.
15. The method of claim 14, wherein the substantially constantly
regulating step includes stopping the feed of said drill stem
during the last stage of an approaching overload condition and
automatically returning the feed to an optimum rate when a
potential overload condition is past.
16. The method of claim 9, wherein the flushing step is performed
by injection of hydraulic fluid through a transfer duct and a
hollow flow passage in said drill stem and bit; and the monitoring
step is performed by sensing the positive gauge pressure of said
hydraulic fluid in said duct using a transducer.
17. The method of claim 16, wherein said hydraulic fluid being
injected for the flushing step includes water.
18. The method of claim 17, wherein during the drilling and
flushing steps the cuttings and dust form a slurry that flows
around the drill stem and bit and out of the drill hole.
Description
[0001] This is a continuation of U.S. patent application Ser. No.
09/198,327, filed Nov. 24, 1998, now U.S. Pat. No. 6,216,800.
TECHNICAL FIELD
[0002] The present invention relates to an improved system for
in-situ drilling, and more particularly, to such a system where the
rate of drilling is regulated by monitoring one or more parameters
of the fluid flow for disposing of the cuttings and dust.
BACKGROUND OF THE INVENTION
[0003] Most earth drilling systems employ some form of rotary or
percussion powered drills. There have been many advances in recent
years to make the drilling operation more efficient, and thus
provide better and faster drilling speeds, especially in rock
layers. Typically, a drilling machine, such as for forming a hole
for an explosive charge, or for anchoring a roof bolt, includes a
drill stem with a drill bit on the distal down hole section
thereof. The stem/bit on a rotary drill machine is rotated by a
spinner mounted on a drill head to form the drill hole. The rotary
driving motion of the spinner is usually hydraulically or
pneumatically driven and manually regulated by the operator of the
drill machine. Due in part to the advances in the technology, such
as in regard to the drill bit and/or components of the drilling
machine, providing attendant easier and faster drilling, operators
have become accustomed to set the controls to try to drill the hole
in the least amount of time. In doing so, the spinner head is
rotated and the feed of the drill head is engaged to move the drill
stem into the hole as rapidly as possible. The operator typically
changes these settings only in the event that a problem
develops.
[0004] As a part of the more efficient drilling, the cuttings and
dust must be collected and removed from adjacent the drill bit so
that clean cutting edges are provided at the bottom of the hole to
allow the most efficient contact with the rock, or other strata.
Typically, a pneumatic or hydraulic cuttings/dust
collection/suppression and removal system is employed. Pressurized
air, or a suitable hydraulic fluid such as water, or an air/water
mixture, is forced down a center passage through the drill stem to
bail or pick up the cuttings and dust for disposal. It is also
known to impose a vacuum on the center passage of the drill stem
drawing air into the hole around the periphery of the drill stem,
whereupon the cuttings and the dust particles are entrained and
removed through the center passage. In either system, this
withdrawn debris is pneumatically or hydraulically conveyed away
from the drill hole. When using air, the cuttings and dust are then
filtered out at a remote location and disposed of. In systems where
water is used, either exclusively or in a mixture with other
fluids, an option is to simply allow the dust to be suppressed and
then deposited outside the drill hole. In either case, airborne
contamination is advantageously substantially eliminated.
[0005] A typical drilling arrangement and cuttings/dust collecting
system is shown in the prior art; Howeth, U.S. Pat. No. 4,434,861.
In this patent, the bailing air is supplied through the center
passage of the drill stem and the cuttings/dust is removed from the
hole by a vacuum head. Insofar as the '861 disclosure is concerned,
the advancement of the drill stem into the hole, and the rotation
of the drill bit, are manually controlled by the operator. Other
functions of the drilling system are however automatically
controlled, such as the extending or retracting the drill stem with
respect to the deck plate. In other words, the drill stem extends
to the drilling position only when the drill stem is supplied with
sufficient bailing air to be operative, and the drill stem is
automatically retracted from the hole when the bailing air supply
is terminated (see column 14, lines 14-37).
[0006] Another feature of the prior art Howeth '861 patent is to
provide an improved vacuum skirt around the hole and the drill stem
so as to attempt to improve the sealing, and thus enhance the
efficiency of the bailing operation by reducing the tendency of the
bailing system to choke or overload. This patent also teaches the
fundamental premise of making certain that the passageways are
proportioned sufficiently larger than the drill hole to also help
alleviate choking of the bailing air carrying the cuttings/dust
(see column 14, lines 38-66). While this overall system is an
improvement over prior art drilling machines, problems still arise
with regard to choking or overloading the vacuum system, especially
where the drill speed is increased beyond normal levels and when
strata containing soft minerals, coal, shale, mud stone or the like
debris are encountered in the drilling operation.
[0007] Other patents, such as the patent to Ek, U.S. Pat. No.
3,946,818, have disclosed other efforts of inventors to improve the
sealing of the skirt in a different manner to try to improve the
flow so that choking does not occur as readily. Heretofore,
approaches other than these stop gap methods to solve the same
problem have simply not been successful, insofar as we are aware.
In theory, the operator of the drilling machine is simply depended
upon to try to anticipate any approaching choking or flow overload
situation and then shut the machine down. Unfortunately, in an
overwhelming percentage of times, this is not possible because of
the response time factor, and the collecting system becomes
overloaded. The entire drilling operation must then be shut down
for an extended period, the drill stem and bit removed from the
drill hole and all passageways cleared of the debris.
Alternatively, drilling must be performed at a continuously reduced
rate to compensate and thus prevent these intermittent overload
conditions.
[0008] Other inventors have concentrated on improving other aspects
of the drilling machines, such as with respect to an improved
cyclone filter, as set forth in the England U.S. Pat. No.
5,320,188. Indeed, there have even been attempts to control the
flow of pneumatic fluid to the drilling tool in an automatic
fashion. In the McDonald et al. U.S. Pat. No. 4,936,397, the
pneumatically controlled valve is operable to transmit an initial,
extra strong pulse of air to initiate operation of the down hole
drilling motor. Once the motor is operating, the valve is kept open
at a lower pressure than is required to open it so that the
drilling can continue at a lower energy level.
[0009] Similarly, energy saving is the impetus in the Enlund et al.
U.S. Pat. No. 5,409,072, wherein the pneumatic air supply is
provided by a compressor driven by a hydraulic drive motor with
adjustable displacement. The pneumatic pressure supplied by the
compressor is adjusted inversely proportional to the pressure
primarily used to drive the percussion drill along its linear path,
and/or the input pressure of the drive motor itself. In this
manner, it is proposed that the energy required to operate the
entire system is maintained substantially constant during all
phases of the operation.
[0010] Thus, while many refinements have been made in drilling
machines and their method of operation, there is a marked absence
of more responsive control systems, and more particularly with
regard to regulating the drill feed and rotation in response to one
or more parameters occurring in the cuttings/dust collecting or
suppression system. Such a concept would have specific usefulness
in improving the drilling efficiency especially for forming small
(20-50 mm) diameter holes using rotary cutting tools and high tool
feed forces. In such an arrangement, we have discovered that it
would be especially advantageous to keep the drill penetration rate
as rapid as possible, while at the same time control the rate of
tool advance and/or rotation using feedback from the cuttings/dust
collection or suppression system. In this manner, it is believed
that clogging or overload, and its deleterious side effects, can be
avoided. What we envision as a need in the underground mining
industry, and particularly for drilling small diameter holes for
installation of roof bolts, explosive charges or the like, is such
an automatic control, but through a system that is simple in design
and operation.
[0011] Accordingly, it is a primary object of the present invention
to provide an improved in-situ drilling system, and related method
having a control system for maximizing drilling efficiency,
primarily by preventing overload through efficient removal of the
cuttings/dust for collection or suppression by means of a flushing
mechanism, and in addition, substantially eliminating airborne dust
contamination.
[0012] It is another object of the present invention to provide a
highly efficient design for such a system and one that is effective
in operation to anticipate overload by sensing a change in an
operating parameter in the flushing mechanism.
[0013] It is another object to provide a drilling system that makes
a provision to sense a parameter of the fluid used for removal of
cuttings and dust, and then through a feed back signal to a
controller regulate the feed rate of the drill head and/or the
rotation of the spinner.
[0014] It is still another object of the present invention to
provide such an apparatus and its method for providing
substantially continuous in-situ drilling, wherein the drill
cuttings and dust are removed from the drill hole, and either
collected and disposed of or suppressed in a highly efficient
manner, with control being dependent upon the change in pressure,
flow or other parameter in the flushing mechanism, so that the
drill stem and drill bit are maintained in an optimum operating
mode.
[0015] Still another object of the present invention is to provide
a drilling system wherein an approved, low power control circuit is
utilized with a programmable controller to monitor the negative or
positive gauge pressure in the fluid flushing mechanism, and
provide a responsive signal to the feed device for the drill head
and/or the rotary drive of the drill stem to efficiently control
the drilling operation to virtually eliminate downtime due to
clogging or overload.
[0016] Yet another object of the present invention is to provide an
apparatus and method of the type described wherein the controller
is programmable to allow adjustment of the approaching overload,
and other conditions of the drilling operation.
[0017] It is still another object of the present invention to
provide a drilling system utilizing a feed device for the drill
head and a rotary spinner for driving the drill stem and the drill
bit, and wherein the rate of feed of the drill head and/or drill
rotation is effectively controlled based on the level of a sensed
parameter of the fluid flushing mechanism so as to detect an
approaching overload condition, whereby drilling system downtime is
avoided.
[0018] Additional objects, advantages, and other novel features of
the invention will be set forth in part in the description that
follows and in part will become apparent to those skilled in the
art upon examination of the following or may be learned with the
practice of the invention. The objects and advantages of the
invention may be realized and attained by means of the
instrumentalities and combinations particularly pointed out in the
appended claims.
[0019] To achieve the foregoing and other objects of the invention,
and in accordance with the purposes thereof, an improved apparatus
and method for controlling the operation of a drill stem and drill
bit based on monitoring the status of the fluid flushing mechanism
is provided. More specifically, the apparatus provides for
substantially continuous in-situ drilling, collecting and disposing
or suppression of the drill cuttings/dust by feedback of the level
of negative or positive gauge pressure maintained in the flushing
mechanism through a programmable controller. The control circuit is
preferably a low power (4-20 ma) electronic circuit that is
approved for all underground mines. Alternatively, a hydraulic or
electro-hydraulic circuit providing a comparable function is
contemplated. The inventive system is targeted primarily for small
(20-50 mm) holes in virtually any type of mining operation,
including soda ash, coal, trona, salt, potash, limestone, gypsum or
the like.
[0020] In this preferred embodiment for carrying out this
principle, there is provided a drill stem having a drill bit, a
drill head for feeding the stem/bit to form the drill hole, a
mechanism for flushing the cuttings/dust from the hole and
conveying it to a remote location. A transducer tracks at least one
parameter of the flow in order to provide a signal to the
controller for regulating the rate of drilling so as to anticipate
an approaching overflow condition. By utilizing such a system, the
cuttings/dust and other debris are efficiently removed to eliminate
or minimize airborne contamination. This objective is accomplished
in a controlled manner without ever reaching an overload condition
in the flushing mechanism that could lead to clogging and downtime
of the drilling system.
[0021] Also, in the preferred embodiment the parameter is sensed
through the transducer coupled to a transfer duct of the flushing
mechanism. The feedback arrangement provides for a corresponding
signal to be generated by the transducer indicative of the pressure
in the duct. In return, the controller is operative to regulate the
operation of the feed device for the drill head to vary the rate of
feed dependent on the signal level. In addition, the drive unit for
rotating the drill stem/bit can be controlled in concert with the
feed.
[0022] Given the objective requirement for simplicity, the flushing
mechanism includes for vacuum generation a standard blower
connected to the transfer duct through a standard filter. The
filter may include tortuous path, cylinder cartridges and/or
cyclone filters. The filters are periodically emptied/cleaned to
dispose of the larger particles of the cuttings, as well as the
smaller dust particles.
[0023] The controller can be used to program and adjust the
threshold of the approaching overload so that maximum drilling
efficiency is obtained for any particular mining, or related
operation, being performed. The window of operation is set to
insure substantially continuous drilling and eliminate false
signals of approaching overload. The upper and lower thresholds of
the gauge pressure in the flushing mechanism can be varied to
establish the optimum rate of feed and/or drilling rotation.
[0024] In an alternative embodiment, the flushing mechanism
utilizes pressurized, fluids, such as including water, that is
pumped through the center passage of the stem/bit. A slurry of
cuttings/dust is formed and forced out of the drill hole for easy
disposal, while in effect suppressing the dust to eliminate
airborne contamination. Any increase in positive gauge pressure is
sensed through the transducer in the transfer duct to anticipate
any approaching overload condition. As in the preferred embodiment,
corrective adjustment is automatically made in the drilling
rate.
[0025] With respect to the related method of the present invention,
the in-situ drilling and collecting or suppressing of the drill
cuttings and dust from the drill hole includes the steps of
drilling the hole with a drill stem and bit, flushing the
cuttings/dust from the drill hole, monitoring at least one
parameter of the flow of the bailing fluid, and regulating the rate
of drilling to control the parameter during both a normal and
approaching overflow condition. By use of this method, the drilling
operation can be continuous as the collection or suppression of
cuttings and dust from the drill hole is carried out in a
controlled manner.
[0026] In accordance with the preferred version of the method, the
parameter being monitored is the vacuum or negative fluid pressure
level in the flushing mechanism. The regulating step is preferably
concerned with the rate of feed of the drill stem into the drill
hole. That is, the feed rate, including from zero to maximum, is
made dependent on the signal level of the negative gauge pressure
sensed in the transfer duct during the step of collecting and
conveying the cuttings/dust or otherwise suppressing the dust. As
an additional feature, the use of a programmable controller, or an
equivalent adjustable operating hydraulic or electro-hydraulic
valve, allows the addition of the step of adjusting the threshold
of the approaching overload of the flushing mechanism for maximum
efficiency. Also, adjustment of the reset window of the gauge
pressure is contemplated. Close control of the threshold and the
reset window helps in establishing the optimum rate of feed for the
drill stem and thus the drilling efficiency. In more specific
terms, in the case of vacuum flushing, the adjusting step is
performed by setting the threshold level of the vacuum/negative
gauge pressure in the range of 10% to 20% above the normal negative
pressure level, and to reset to normal vacuum within 0.5-4 inches
Hg. as the threat of the overload is passed. If desired, the
regulating step can include changing the speed of the rotary
driving of the drill stem, also depending on the signal level from
the transducer and coordinated with the linear feed rate of the
drill stem.
[0027] Thus, under optimum operating conditions, the regulating
step can perform so as to maintain the parameter in the flushing
mechanism, such as the vacuum level or rate of flow of the fluid,
so as to be substantially constant. Also, while the regulating
step, as controlled by the programmable controller, can be made to
vary the drill head feed and the spinner rotation, the preferred
embodiment at present is to actually stop the feed of the drill
stem and/or the spinner during an approaching overload condition,
and to automatically restart the feed/rotation at the optimum rate
when the potential or threatened overload condition is past.
[0028] Still other objects of the present invention will become
readily apparent to those skilled in this art from the following
description wherein there is shown and described a preferred
embodiment of this invention, simply by way of illustration of one
of the modes best suited to carry out the invention. As it will be
realized, the invention is capable of other different embodiments,
and its several details are capable of modifications in various,
obvious aspects all without departing from the invention.
Accordingly, the drawings and descriptions will be regarded as
illustrative in nature and not as restrictive.
BRIEF DESCRIPTION OF THE DRAWING
[0029] The accompanying drawing incorporated and forming a part of
the specification, illustrates several aspects of the present
invention, and together with the description serves to explain the
principles of the invention.
[0030] FIG. 1 is a schematic diagram of the drilling system of the
present invention, including its preferred flushing mechanism and
control circuit, and as applied to a rotating drill stem/bit for
forming a drill hole in the earth having variable strata; and
[0031] FIG. 2 is a similar schematic diagram of the alternative
embodiment using a pressurized hydraulic fluid for flushing the
drill hole for suppression of the dust, rather than a vacuum for
flushing and remote disposal.
[0032] Reference will now be made in detail to the present
preferred embodiment of the invention, an example of which is
illustrated in this drawing.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0033] With reference now to FIGS. 1 and 2 of the drawing, an
in-situ drilling system is illustrated that represents in a
graphical fashion the important aspects of the present invention,
both in the apparatus and method form, and in the preferred and
alternative embodiments. The particular representation of the
preferred FIG. 1 embodiment is typical of drilling in a mine roof
having rock strata S.sub.1 forming the ceiling of a mine.
Additional overburden includes representative seams of mud S.sub.2
and soft rock/mineral or gravel S.sub.3; it being understood as
pointed out above that this representation is merely one
environment in which the drilling system of the present invention
can be utilized. A drill stem 10 with a drill bit 11 formed on the
distal, down hole point of the stem is forming a drill hole, such
as for placement of a roof bolt (not shown). The drill stem 10 is
fed into the hole by force supplied by drill head 15, and the
rotation to cause the drill bit 11 to cut the rock is provided by a
rotary spinner 16. While this representative embodiment features a
rotary drill, it is to be understood that in accordance with the
broadest aspects of the invention, other forms, such as percussion
drilling could be used. Also, in the drilling system of the present
invention, the preferred range of the diameter of the drill hole is
20-50 mm; however, it is to be understood that other size holes can
also be drilled using the same principles. Of course, in addition
to drilling in overhead strata, the system of the present invention
could be used in a side wall, or in the floor of any earth strata,
as represented in the alternative embodiment of FIG. 2, and for
other purposes, including placement of explosive charges and the
like.
[0034] The drill stem 10 and the drill bit 11 include a central
passage 20 and the proximal end includes a coupling 21 for
connection to a transfer duct 22. A filter 23 is positioned in the
transfer duct to collect the cuttings and the dust formed by the
drill bit 11 cutting into the rock (see upstream particle
representations in the drawing). Downstream, a blower 24 with the
intake side connected to the filter 23 establishes the vacuum or
negative gauge pressure through the filter 23, the transfer duct 22
and the drill stem/bit 10, 11. These components together form a
preferred embodiment of a flushing mechanism for the cuttings/dust
that is bailed and removed from the bottom of the drill hole 12. As
will be apparent, the bailing air flow established by the vacuum in
the transfer duct 22 enters through the annular opening around the
drill stem 10 and drill bit 11, picks up and removes the
cuttings/dust particles and conveys the same to the filter 23 at a
remote location. Periodically, the filter 23 is emptied and cleaned
allowing the cuttings/dust to be disposed of.
[0035] In accordance with an important aspect of this preferred
version of the present invention, a vacuum or negative gauge
pressure transducer 30 is tapped into the transfer duct 22 to
monitor this parameter of the flow of the cuttings and dust. While
the transducer 30 is the preferred component for monitoring the
flow, other sensors could be substituted for monitoring different
parameters, such as for example the actual flow rate of the bailing
air as it passes through on the way to the filter 23. The
transducer 30 provides an output signal over line 32 that
represents the parameter being monitored in the transfer duct 22. A
programmable controller 33 receives the signal and in a manner as
will be more apparent in the description below, provides for
regulating the rate of drilling by the drill bit 11.
[0036] The controller 33 is programmed to establish a normal
drilling rate, and as long as the drill bit remains in the same
rock strata S.sub.1, this condition is not changed. However, upon
entry into another type of strata, such as the soft mud strata
S.sub.2, the soft rock/mineral/gravel strata or other debris
S.sub.3, a controlled change is automatically made in accordance
with the present invention. To do this, the controller 33 is
connected by signal line to a drill head feed device 36, which as
shown acts to apply linear force against the drill head 15. A
pneumatic or hydraulic power source (not shown) provides this force
that simply acts to push the drill head 15 into the drill hole 12
at a substantially constant rate. The constant rate continues until
the drill bit 11 breaks through to the softer stratas S.sub.2,
S.sub.3, at which time the threat of overload of the flushing
mechanism 20-24 occurs.
[0037] According to the principles of the present invention, the
controller 33 through the transducer 30 senses this approach of the
overload condition, and in response reduces the rate of feed
supplied by the feed device 36. With the feed rate thus reduced,
the passage 20 and the flushing mechanism 20-24 can recover by
increasing the percentage of bailing air with respect to the
mud/soft rock/gravel or the like that suddenly is entering through
the passage 20. As a result, choking or overload of the flushing
mechanism 20-24 is avoided and the operation of the drilling system
can continue as programmed in the most efficient manner.
[0038] To explain further, in the past prior to the present
invention, the soft strata material, especially if wet, would
immediately tend to clog the passage through the stem/bit. When an
adjustment is not made, the vacuum system in general, and any
flushing mechanism in particular, could not remove the
cuttings/dust fast enough to prevent solid plugging. When this
occurs, the drill bit is isolated from the distal cutting face of
the hole by the debris so that effective drilling cannot continue.
Furthermore, such plugging as has occurred often in the past
requires costly downtime for removal of the stem/bit from the hole
and tedious cleaning of the entire flushing mechanism.
[0039] The controller 33 can be programmed in any suitable manner,
such as through a manual control 35, and more specifically a key
board. The rate of movement of the drill stem/bit 10, 11 being
forced by the feed device 36 into the drill hole 12 can be
regulated to slow to the degree necessary to allow the level of
vacuum in the transfer duct 22 to recover to a safe, lower negative
gauge pressure once the threat of overload has passed. However, a
preferred, and broadly equivalent embodiment for the purposes of
explaining the present invention, the forward advance of the feed
device 36 is stopped during the regulation step. The controller 33
can set the threshold level at any desired point in order to safely
anticipate the overload condition, and thus stop the feed in time
to prevent the deleterious choking and clogging of the system that
would otherwise require time consuming and expensive shutdown.
[0040] Typically, the vacuum or negative gauge pressure is set at a
threshold level of approximately 10-20% higher than the normal
operating level of 10-18 inches Hg. This advantageously establishes
the overall optimum rate of feed since the point of overload is
never reached in practice. The reset level of the negative pressure
is in the range of 0.5-4 inches Hg. These typical ranges do vary
for different types of mines, or other applications, where the
strata and operation conditions can vary significantly.
[0041] The controller 33 is also preferably connected to rotary
drive unit 40 over signal line 41 that is connected to the spinner
16. As with the feed device 36, the drive unit 40 is understood to
be connected to a power source, either pneumatic or hydraulic, in
order to rotate the spinner 16. In addition to stopping or slowing
the drill head feed, within the broadest aspects of the present
invention the same and/or complimentary effect of preventing
overload of the flushing mechanism 20-24 can be accomplished by
coordinated regulating the speed of the spinner. In other words, by
reducing the rotation of the drill bit, the amount of cuttings/dust
and debris can be reduced instantaneously upon sensing a rise in
the negative gauge pressure, thus giving the flushing mechanism
time to recover to normal, lower negative pressure levels. Of
course, as mentioned above, rather than a rotary drill, within the
broadest aspects of the invention a percussion or other type drill
can be used and drilling rate regulated.
[0042] The controller 33 can also activate an alarm 45 for the
benefit of the operator of the roof bolting or other machine, that
incorporates the drilling system of the present invention. Also, as
a precaution, a relief valve 46 can be provided on the blower 24 in
order to prevent excessive vacuum from being generated in the
unlikely event of a catastrophic overload occurring.
[0043] In the alternative embodiment of FIG. 2, the key difference
is the substitute of a hydraulic pump 50 for the blower 24, and
pressurized water or other hydraulic fluid is used for flushing,
instead of the vacuum and air. As illustrated, the like components
are designated by the same reference numerals but including a prime
designator. As is clear, the pressurized water (including water/air
mixture, if desired) from pump 50 is forced through the transfer
duct 22' and through the passage 20' of the stem/bit 10', 11'. A
slurry of cuttings/dust is formed, forced out of the drill hole
around the stem/bit and deposited on the floor. The dust that would
otherwise provide airborne contamination is suppressed due to the
wet condition of the slurry. The controller 33' in response to the
positive gauge pressure monitored by the transducer 30' controls
the feed device 36' and/or the drive unit 40' in the event that the
back pressure signals an approaching overload due to clogging by
debris, such as from the strata S.sub.2', S.sub.3'. An alarm 45'
signals the presence of the overload condition to the operator.
[0044] The related method of the present invention for in-situ
drilling and flushing of the drill cuttings and dust includes the
steps of drilling the hole with the drill stem/bit 10, 11 or 10',
11', feeding the same into the earth by the feed device 36, 36'
acting on the drill head 15, 15' as the bit 11, 11' is effective to
form the hole, flushing the cuttings/dust by bailing fluid flow
through the flushing mechanism 20-24; 20', 22', 50 monitoring at
least one parameter of the flow, such as negative or positive gauge
pressure, and regulating the rate of drilling through the
controller 33, 33' by a feedback signal to avoid an approaching
overload condition if it occurs. As a result of this method, the
cuttings/dust are collected or suppressed in a controlled manner,
and in a substantially continuous drilling operation, providing for
increased efficiency in any roof bolt/explosive charge
installation, or related drilling operation.
[0045] In the preferred method, the parameter being monitored is
the level of vacuum in the bailing air flow through the transfer
duct 22. Once the vacuum level is raised due to an approaching
overload condition, the feed of the drill head 15 is advantageously
stopped, or reduced proportionally to the requirement that is
sensed, in response to the rise in the vacuum/negative gauge
pressure level. At any time, the particular threshold level where
the feedback signal stops or reduces the feed can be reprogrammed
through the manual control 35.
[0046] In addition, in the illustrated embodiments the regulating
step may include stopping or reducing the speed of rotation of the
spinner 16, 16' through the rotary drive unit 40, 40' upon sensing
an increase in the gauge pressure by the transducer 30, 30' to the
threshold level. In this instance, the controller 33, 33'
coordinates the speed regulation through the spinner 16, 16' with
the feed regulation of the feed device 36, 36' through the drill
head 15, 15'. As in all instances of the method, once the potential
overload condition is past, the feed and/or rotation of the drill
stem 10, 10' and the drill bit 11, 11' is automatically returned to
the optimum rate.
[0047] The programmable controller 33, 33' preferably includes a
PLC or microprocessor that operates in a 4-20 milliamp low power
range and approved for all types of mines by MSHA. Indeed, it is
contemplated that the controller 33, 33' can be combined with
various other sensors of the drilling system being monitored in
order to help in regulating the entire drilling operation. As
necessary, the operator of the roof bolting machine, or other
machine where the drilling system is utilized, can use manual
controls 35, 35' to override or assist the automatic control of the
control circuit of the present invention. However, the most
significant advantages are attained by automatically anticipating
an overload of the flushing mechanism 20-24; 20', 22', 50,
supplying the bailing fluid, and thereby enhancing productivity of
the drilling operation. The greatest benefit is in reducing
downtime that would otherwise be needed to remove the drill
stem/bit 10, 11; 10', 11' and clear the passageways of the flushing
mechanism.
[0048] When working in soft minerals, such as trona, the negative
or positive pressure levels detected in the transfer duct 22, 22'
run comparable to drilling through strata of limestone, coal, shale
or sand stone, or other debris such as in a coal mine. In other
words, the trona as a soft mineral still requires no higher
threshold level than in a normal bailing operation. As this feed
back signal level is increased, the limiting factor to the speed of
forming the drill hole 12 becomes maintaining the flushing
mechanism 20-24; 20', 22', 50 of the present invention operating
continuously, and the system of the present invention is able to do
this. By incorporating the 10-18 inches Hg. operating threshold
level, and the 0.5-4 inches Hg. reset window or range, the problem
of clogging and the attendant downtime is virtually eliminated in
this type of mine operation. Generally, the lower the threshold
level and the narrower the reset window, the more efficient
operation is attainable. Also, while the threshold/reset control is
contemplated as being efficiently handled by the controller 33, 33'
equivalent threshold pressure/reset switches can be incorporated
directly with the feed device 36, 36' and/or the drive unit 40, 40'
if desired.
[0049] In summary, the drilling system of the present invention for
continuously in-situ drilling and flushing of the drill
cuttings/dust operates in a manner to provide maximum drilling
efficiency. The drill stem/bit 10, 11 or 10', 11' feeds into the
drill hole in a controlled manner through the operation of the feed
device 36, 36' as controlled in response to the programmable
controller 33, 33'. A flushing mechanism 20-24; 20', 22', 50
provides bailing fluid into the drill passage 20, 20' and picks up
the cuttings/dust in a highly efficient manner for disposal. By
sensing the negative or positive gauge pressure through the
transducer 30, 30', the controller 33, 33' regulates the
advancement of the drill head 15. Because the controller is
programmed to anticipate an overload condition in the transfer duct
22, 22' the drilling can proceed without deleterious downtime. In
addition to the feed of the drill head 15, 15', the spinner 16, 16'
of the drill stem/bit can be regulated by the controller 33,
33'.
[0050] The foregoing description of the preferred embodiment of the
invention has been presented for purposes of illustration and
description. It is not intended to be exhaustive or to limit the
invention to the precise form disclosed. Obvious modifications or
variations are possible in light of the above teachings. The
embodiment was chosen and described to provide the best
illustration of the principles of the invention and its practical
application to thereby enable one of ordinary skill in the art to
utilize the invention in various embodiments and with various
modifications as are suited to the particular use contemplated. All
such modifications and variations are within the scope of the
invention as determined by the appended claims when interpreted in
accordance with the breadth to which they are fairly, legally and
equitably entitled.
* * * * *